Unlike so many of Britain's leading art collectors in the past, Charles Saatchi thrives on backing young, emerging and hugely provocative talent. Aristocrats weaned on the Grand Tour Þlled their resplendent homes with foreign artists as venerated as Raphael, Titian or Rembrandt, most of whom had died long before. In the early 20th century, when modern art was at its rebellious zenith, the most outstanding British collector was Samuel Courtauld. Concentrating on French art from Manet to Cezanne, he completely ignored the greatest painters of his own generation.

Saatchi, however, broke the mould. Far from shunning untested and controversial artists, he scoured the colleges for promising students. He was excited by the idea of discovery. His restless appetite for the new made him quick to detect exceptional promise in the graduates of Goldsmiths College, who held an ambitious show in the old Port of London Authority building in London's Docklands. The year was 1988 and the three-part Freeze exhibition was masterminded by an unknown Goldsmiths student called Damien Hirst.

Some of the 16 artists on view lacked the impact that they would later command, and even Hirst was not yet hard-hitting. But Saatchi warmed to the chutzpah behind the show as a whole. Sponsored by the London Docklands Development Corporation, it chimed with the accelerating mood of conÞdence in the long-blighted East End.

Hirst and his feisty contemporaries - among them Ian Davenport, Anya Gallaccio, Gary Hume, Michael Landy, Sarah Lucas and Fiona Rae - demanded to be seen. Among the diverse range of exhibits displayed in Freeze, some already had the power to unnerve. Mat Collishaw's close-up photograph of a bullet hole piercing a human head, illuminated from behind in an advertising light-box, was a haunting and gruesome image. It inspired the exhibition's arresting name, for the catalogue declared that Collishaw's Bullet Hole was 'dedicated to a moment of impact, a preserved now, a freeze-frame'.

The chilling word caught on, even if Gary Hume associated the show's opening with an outburst of extreme, dangerous heat. A Þre broke out in a nearby tower block, and Hume recalled looking across at the 'smoke and billowing' flames, thinking they were a 'torch lit for our exhibition - it seemed like a portent'.

He was correct. Freeze soon acquired a legendary aura, and Saatchi played a decisive role in ensuring that its participants began to seize wider attention. Apart from his spending power and his promotional savvy as a seasoned advertising man, he had one invaluable asset: a recently converted gallery where the new generation could be displayed with the maximum amount of visual punch. He had opened this spectacular showcase in 1985.

The building was a large yet run-down paint factory in St John's Wood, miles from the areas of London where most art galleries could be found. But the conversion was stunning enough to ensure that the Saatchi Gallery attracted plenty of awed and excited visitors. At that time most private galleries staged their exhibitions in cramped, undistinguished premises. But Saatchi offered an eye-blinding acreage of wide, lofty spaces, with white floors matching the equally brilliant white walls.

The inaugural shows were dedicated to classic US artists from the post-war period, with Andy Warhol's brazen pop icons and Don Judd's severe minimalist boxes prominent among them. But by the time Saatchi staged a two-part survey of New York Art Now, between 1987 and the following year, he was showing young blood as controversial as Robert Gober and the notorious Jeff Koons. Objects coolly suspended in vitrines dominated Koons' contributions and they must have fascinated the fledgling Damien Hirst. But when he exhibited his tiger shark suspended in a tank of formaldehyde, part of a landmark Saatchi Gallery show of 1992, Hirst revealed his wholly personal obsessions. He called the silent, mesmerising shark The Physical Impossibility of Death in the Mind of Someone Living. And the optical illusion of movement, generated by its abrupt shifts of position behind the glass as awed visitors walked round the tank, suggested that the shark was still, somehow, alive.

No such fantasy could be entertained by anyone in front of another Hirst exhibit, A Thousand Years. In one half of its double-glass cube, a white box contained a breeding ground for maggots by the thousand. But once the bluebottles flew out, they were trapped inside the steel-framed container. So the hapless flies were forced to alight on a rotting cow's head abandoned on the floor. Above it the glowing tubes of an insectorcutor lay in wait, its tray already strewn with dead insects.

Sculpture is here transformed into a charnel house. Like the gloomiest of Jacobean playwrights, Hirst announced his overriding preoccupation with mortality. It was a relentless pursuit, leading him to slice up animals into sections and exhibit the results, with clinical clarity, in containers that offer onlookers no escape from the exposed cadaver. The frieze-like position of the animals links Hirst with the neoclassical tradition, and in particular with George Stubbs' determination to dissect the anatomy of a horse. But many commentators, above all the tabloid press, seized on Hirst's seemingly heretical stance. Their viliÞcation soon made him notorious, the most well-known artist of his generation.

The truth was, though, that several outstanding contemporaries shared his involvement with death. As if in defiance of the widely held notion that young people are unaware of decay and the grave, Marc Quinn poured eight pints of his own blood into a cast of his head. When frozen and installed in a perspex cube powered by a refrigeration unit, he exhibited his head with the raw, direct title Self. Like Hirst's link with Stubbs, Quinn's sculpture can be related to a cast of William Blake's face, an image that had already inspired some of Francis Bacon's spectral paintings. But Self was unsettling enough to attract an enormous amount of hostile publicity. The interest in Young British Artists, or YBAs as they were often nicknamed, was growing feverish. And Saatchi, avoiding interviews himself, knew exactly how to fan the media flames for the artists he admired.

Not all the work in his prodigious, rapidly expanding collection depended on startling new materials or working methods. Jenny Saville, a graduate of the Glasgow School of Art, won Saatchi's devoted attention with old-fashioned oils on canvas. Even so, the immense bulk of the female bodies she painted was disturbingly oppressive. Saville compounded the alarm by marking the naked women's flesh with lines, suggesting preparations for a surgeon's scalpel. Sarah Lucas shared this interest in overweight females. In her case, however, the raw material was culled from shameless Sunday Sport stories about 'obese housewives' and so-called 'topless midgets'. Lucas was fascinated by crude caricatures of women's sexuality. She affronted many viewers with her in-your-face installations of two fried eggs and a kebab, or melons above an empty water-bucket slung on a shabby mattress.

This frank involvement with the seedy side of life explains why Lucas collaborated with Tracey Emin for a while on running an East End 'rude girl' boutique called, with typical bluntness, The Shop. Saatchi's immaculate white arena in St John's Wood could not hope to match the blatant wallowing in dingy confessional revelations. But he lost little time in acquiring Emin's blue tent, appliqued with the names Everyone I Have Ever Slept With 1963-1995.

'Tracey', as she was swiftly dubbed by reporters avid for her turbulent memories of a Margate girlhood and adolescence, even included the name of the foetus she aborted. No conventional limits were placed on her willingness to disclose the pain and humiliation she had suffered.

When Emin displayed her own soiled, rumpled bed in the Turner Prize show, this readiness to break down the barriers between art and life brought her a notoriety equal to, and possibly greater than, Damien Hirst. 'Tracey' had become an instantly recognisable part of contemporary British culture, and Saatchi did everything he could to magnify her fame.

The most heated of all his attempts to drive YBAs into the national consciousness occurred in 1997, when Sensation opened at the Royal Academy. With hindsight, we can see that it prophesied Saatchi's current decision to invade the civic grandiloquence of County Hall. For the Royal Academy's architecture was almost as far removed from the purged, glacial simplicity of the Saatchi Gallery. If anything, Hirst and his cohorts became still more startlingly irreverent within the Academy's portals. The statue in the courtyard, of the RA's president Sir Joshua Reynolds, with his palette in hand, seemed to stand aghast. And the most virulent attack was aimed at Marcus Harvey, whose monumental painting of the Moors murderer Myra Hindley was covered with children's hand-prints. On Sensation's subsequent international tour the focus of indignation shifted. In New York, Chris Ofili's Holy Virgin Mary, replete with elephant dung and pornographic imagery, made Mayor Giuliani threaten to slash the city's $7.3 million subsidy to the Brooklyn Museum where Sensation was staged. Saatchi, however, thrives on hysterical controversy. He wants to demolish taboos, in the hope of widening art's ability to explore human life with frankness, daring and verve. All the signs are that his subversive manoeuvres will continue unabated at his new, deceptively respectable headquarters beside the Thames.

· Richard Cork's four books on modern art from 1970 to 2000 will be published by Yale in May